import cv2
import numpy as np

img = np.zeros((480, 640, 3), np.uint8)
# cv2.ellipse(img, (320, 240), (100, 50), 0, 0, 360,  (0, 0, 255))
cv2.ellipse(img, (320, 240), (100, 50), 0, 0, 180,  (0, 0, 255))
cv2.ellipse(img, (320, 240), (100, 50), 90, 45, 90,  (0, 0, 255), -1)
while True:
    cv2.imshow('ellipse', img)
    key = cv2.waitKey(10)
    if key & 0xFF == ord('q'):
        break

cv2.destroyAllWindows()
